The overall plan of this research program is twofold: to elucidate the pathophysiolgy of malabsorption in AIDS entero-athy and eventually to formulate rational therapy, and to clarify the physiology of small intestinal absorption in general. Our unique kinetic model of D-xylose absorption will be used. I.Rationale: Using a kinetic model, we have recently completed studies on D-xylose absorption in patients with renal insufficiency, suspected malabsorption, AIDS enteropathy, and normal controls (1-5).